Cache configuration in a database system

1. A computer-implemented method for providing workload windows in a database system having at least one cache fragment, the method comprising: collecting cache-efficiency-indicator values of an at least one cache fragment during operation of a database system over a period of time; providing approximation-function-parameter values for the collected, cache-efficiency-indicator values calculated with an approximation function as exp(c*x) where c is a negative parameter and x is a size of the at least one cache fragment; providing a set of workload windows based on the approximation-function-parameter values; providing workload-window information for the set of workload windows, the workload-window information including at least one approximation-function-parameter value representing each member of the set of workload windows; storing the workload-window information for a comparison based on the collected cache-efficiency-indicator values and the workload-window information; selecting a workload window having first workload-window information matching the approximation function modelling a set of current cache-efficiency-indicator values; and adjusting cache configuration based on the first workload-window information of the selected workload window.

2. The computer-implemented method of claim 1 wherein providing the set of workload windows comprises finding time periods where the approximation-function-parameter values remain substantially constant.

3. The computer-implemented method of claim 1 further comprising discarding a potential workload window if the duration of the potential workload window is shorter than a predefined value.

4. The computer-implemented method of claim 1 , wherein the workload-window information comprises at least one of the following: start time of a workload window, stop time of a workload window, and statistical information about the approximation-function-parameter values within the workload window.

5. The computer-implemented method of claim 1 further comprising: providing a set of current, cache-efficiency-indicator values for the at least one cache fragment; and modelling the current, cache-efficiency-indicator values for each cache fragment with an approximation function.

6. The computer-implemented method of claim 5 , comprising updating the workload-window information based on the set of current, cache-efficiency-indicator values.

7. A database system comprising at least one cache fragment and a cache controller, the cache controller configured to: collect cache-efficiency-indicator values of the at least one cache fragment over a period of time; provide approximation-function-parameter values for the collected, cache-efficiency-indicator values calculated with an approximation function as exp(c*x) where c is a negative parameter and x is a size of the at least one cache fragment; provide a set of workload windows based on the approximation-function-parameter values; provide workload-window information for the set of workload windows based on the collected, cache-efficiency-indicator values, the workload-window information including at least one approximation-function-parameter value representing each member of the set of workload windows; store the workload-window information for a comparison based on collected cache-efficiency-indicator values and the workload-window information; select a workload window having first workload-window information matching the approximation function modelling a set of current cache-efficiency-indicator values; and adjust cache configuration based on the first workload-window information of the selected workload window.

8. The database of claim 7 , wherein providing the set of workload windows comprises finding time periods where the approximation-function-parameter values remain substantially constant.

9. The database of claim 7 further comprising discarding a potential workload window if the duration of the potential workload window is shorter than a predefined value.

10. The database of claim 7 , wherein the workload-window information comprises at least one of the following: start time of a workload window, stop time of a workload window, and statistical information about the approximation-function-parameter values within the workload window.

11. The database of claim 7 further comprising: providing a set of current, cache-efficiency-indicator values for the at least one cache fragment; and modelling the current, cache-efficiency-indicator values for each cache fragment with an approximation function.

12. The database of claim 11 comprising updating the workload-window information based on the set of current, cache-efficiency-indicator values.

13. A computer program product comprising a non-transitory computer-readable medium including a non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium when executed on a data processing system causes the data processing system to: collect cache-efficiency-indicator values of at least one cache fragment over a period of time; provide approximation-function-parameter values for the collected cache-efficiency-indicator values calculated with an approximation function as exp(c*x) where c is a negative parameter and x is a size of the at least one cache fragment; provide a set of workload windows based on the approximation function parameter values; provide workload-window information for the set of workload windows based on the collected cache-efficiency-indicator values, the workload-window information including at least one approximation-function-parameter value representing each member of the set of workload windows; store the workload-window information for a comparison based on the collected cache-efficiency-indicator values and the workload-window information; select a workload window having first workload-window information matching the approximation function modelling a set of current cache-efficiency-indicator values; and adjust cache configuration based on the first workload-window information of the selected workload window.

14. The computer program product of claim 13 , wherein providing the set of workload windows comprises finding time periods where the approximation-function-parameter values remain substantially constant.

15. The computer program product of claim 13 further comprising discarding a potential workload window if the duration of the potential workload window is shorter than a predefined value.

16. The computer program product of claim 13 wherein the workload-window information comprises at least one of the following: start time of a workload window, stop time of a workload window, and statistical information about the approximation-function-parameter values within the workload window.

17. The computer program product of claim 13 further comprising: providing a set of current, cache-efficiency-indicator values for the at least one cache fragment; modelling the current, cache-efficiency-indicator values for each cache fragment with an approximation function.

18. The computer program product of claim 17 , comprising updating the workload-window information based on the set of current, cache-efficiency-indicator values.